Is parental cohabitation associated with difficult transitions to adulthood? Although there has been considerable research on the important question of the consequences of parental divorce and remarriage on children's well being, little-to-nothing is known about the effects of cohabitation, despite the fact that children's experience living with a cohabiting parent rapidly increased in recent years. Most research examining the effects of divorce and remarriage have ignored cohabitation, equating cohabiting families with single-parent families. Since the majority of remarriages are preceded by cohabitation, this omission may threaten the validity of past work. This research improves our understanding of the relationship between family experiences during childhood and the transition to adulthood by carefully distinguishing experience in a cohabiting family from experience in a single- parent family, by distinguishing cohabiting families where mother's partner is the biological father of the child from cohabiting families where the partner is not the father, and by including transitions into and out of cohabitation in measures of family instability. The project's aims are to a) construct measures of children's experience in cohabiting households and test the reliability of these measures, b) calculate period estimates of children's recent experience in cohabiting households, c) model the relationship between childhood family structure and educational attainment, premarital fertility and union formation, and d) model the relationship between family instability and educational attainment, premarital fertility and union formation. To accomplish these goals this project uses data from the National Survey of Families and Households and the National Survey of Family Growth. The NSFG respondents provided information on their living arrangements throughout childhood and complete information each of the outcome variables, educational attainment, premarital fertility, and union formation. For the focal children of female NSFH respondents, who became respondents in the second wave (1992-94), we also have information about their mother's martial-cohabitation history and each of the measures of the transition to adulthood. Proportional hazard models will contrast children who experience parental divorce, cohabitation, and remarriage to children who live with both parents throughout childhood.